Verifying your world - 100% - Upload failed (-1)

I'm attempting to upload an older world to a PC Realm I just resubbed to. The world directory is about 4.25 GB, so it takes a while to upload. I've attempted to upload several times, and after it gets to 100% and is going through the verification process, it stops and gives an error "Upload Failed (-1)" I'm happy to provide additional log files if they would be helpful, but since the upload appears to be completing and it's the verification that seems to be the failure (which I assume is server side?) I don't know what direction to go with this. It seems to me that bringing old worlds back from the dead should be Realms' specialty, so I assume this is something you guys would like to work out. Let me know, happy to help!